Modern, moveable aircraft canopies contain many parts. The transparent portion of the canopy will be replaced several times during the life of an aircraft due to scratches and general deterioration. Transparency replacement requires costly frame disassembly and reassembly.
Attempts have been made to produce frameless aircraft canopies with little success. The frame provides structural stiffness and strong, secure, attachment points for hinges and latches. Any viable frameless canopy system must include a method for latching. Prior latching methods consisted of a male hook or pin located on the aircraft structure or canopy frame and a female receiver on the canopy frame structure or aircraft structure respectively. Such discrete latching methods produce concentrated loads, which cause bearing stress in the transparency in the region of the latch.
Glassy polymers craze at low stress levels. The effect of crazing on crack growth and localized failure is not well understood. Polymer transparencies yield at low stress levels and creep occurs after a fraction of service life. Cyclic, long-term loading, such as cockpit pressurization, induces creep and/or craze and reduces service life. Elevated temperatures, such as those experienced by high-speed aircraft, further increase the rate of creep and amplify the effect of crazing.
Therefore, there exists an unmet need to produce a latching system for a frameless canopy, which avoids plastic creep, and crazing due to concentrated loads yet securely holds the canopy in place.